Add UseCounters for <dialog> + CloseWatcher changes

If we are to ship the current integration of CloseWatcher with <dialog>,
we will be:

* Sometimes closing multiple dialogs, when a close signal comes in and
  multiple <dialog>s have been created without user activation.

* Sometimes not firing the cancel event, if the <dialog> was created,
  never interacted with, and then closed via a close signal.

Both of these are technically backward-incompatible changes. However,
they should only occur when a website is doing something relatively
unusual. So, this change adds UseCounters to see how often these cases
occur, so we know whether to push for shipping this, or reconsider our
strategy.

This patch was started here:
https://chromium-review.googlesource.com/c/chromium/src/+/3711968

Fixed: 1383001
Change-Id: Ic0f5cd6d2ea5bcb06d1711f51327749386f88e51
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4084041
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Auto-Submit: Joey Arhar <jarhar@chromium.org>
Reviewed-by: Domenic Denicola <domenic@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1081076}